Means for and method of blast furnace back drafting



Sept. 27, 1932. c, H HE|$T ET AL 1,879,230

MEANS FOR AND METHOD OF BLAST FURNACE- BACK DRAFTING- Filed Sept. 25, 1931 IN VEN TORS. CHARLES H. HEIST 3y BUFORD MSTUBBLEFIELD A TTORNEYS.

Patented Sept. 27, 1932 UNITED STATES cmLEs H. mm, or YOUNGSTOWN,

MEANS For. AND METHOD or BLAST rUnNAcn ack DnArmiNe Application filed sep' emberaa 193 1; seriai'iwo; 564,49o1

The present invention is particularly di-' rected to providing means'for and method of relieving the internal pressure in a blast furnace to effect the operation known as fback drafting which is carried out from time to time in the course of blast furnace operation for the purpose ofcfacilitating repairs to thev seriously endanger the workmen who may be stationed nearby, hinder the executionof' the repairs and sometimes'set fire to inflammable objects in the vicinity.

In most plants it has therefore been the practice to divert the air supply from the hot stoves and to connect one or more stoves with v the draft through the stack drawing air and gases from the furnace through the stove 01-1 stoves thus connected therewith. The reversal of the furnace draftin this manner is commonly referred to as back drafting and in general, is effected by operating a valve disposed in the main, leading from the air blower to the hot stoves to disconnect the blower therefrom and opening the usualffiue.

valve or damper to connect the stoves with the stack, so that the draft through the latter becomes eft'ecive to withdraw residual air and furnace gases from the hot blast main andthe furnace through the stoves and discharge them into the atmosphere through the stack. The hot stoves to which reference has been made comprise large chambers filled with checker bricks which are ordinarily heated by the combustion of a gas and then used to heat a current of air forced over the hot checkerbricks after thegas has been shutoff, suit to conduct the air, thus highly heated, fig- 5m;

the stoves to thefurnace. 1 The improved methods'of gas cleaning "and other features now in vogue combine to permit hot stove checker Work having relatively small interstices therethrough" to be satisfactorily em ployed, but as it is obvious that the resistance offered to the flow of gases thereby is appreciably greater than when relatively large passages are provided in the :checke'r'work, we

have found that satisfactory back drafting'is extremely diflicult, if not impossible, when" the passages through :the checker work in the stoves are thus relatively restricted or iflt-h'ey' become somewhat clogged after long use and the method 'hereinabove described is employed.

' The tion, therefore, is to provide means which will enable "the back drafting of the furnace'toibe effectively. carried out independently of the hot stoves and without the necessity of drawing gas from'the furnacetherethrough .in

order to relieve-the pressure within the latter.

A further object of ourinvention is to provide simple, convenient, cheap, and easily operated ba'c'k'draftingmeanswhich are not AND 'iauronia iii. fsrumatnrrnnn, 0150mmonIo' V n principal object of the present invenlikely to get out of order and which may be so constructed as to be substantially freesfrom the necessity of repair or .replacement throughout the useful lifeof thefurnace with which they are associated. 1'

Another object of our invention is to pro: vide an improved method-for backdraftin'g ablast furnace in which the necessity for withdrawing gases from the furnace through the'stovesis' avoided and the gases withdrawn from :the furnace are introduced dire'c'tly'into the stack and disposed of 'therethrough.

Other purposes, objects and advantages of our invention will'he-reinafter more fully 'a'ppear or be understood from the following de-" scription of certain apparatus-embodyingour V invention and of our improved method of carrying out the back 'drafting'operation,

reference being had to the aocompanying drawing.

In the said drawing, Fig. --1 'is a diagrammatictop plan view of a blast furnaeeand certai-Tn'other apparatus connected therewith adapted for the purposes of our invention; Fig. 2 is a fragmentary detail in top plan view on an enlarged scale of certain of the parts shown in Fig. 1, and Fig. 3 is a similar view thereof principally in side elevation. In the several figures like characters are used to designate the sameparts. 9

Referring now more particularly to the drawing, the apparatus diagrammatically represented in Fig. 1 includes a blast furnace 1 of the usual or any preferred type which is connected to a series of hot stoves 2 through a hot blast main 3 by means of usual connections 4 leading respectively fromthe several stoves into the main, the stoves 2 also being connected to a sewer 5 adapted to carry exhaust gasesfrom the several stoves into the stack 6, suitable valves (not shown) being customarily provided in the connections 4 for cutting off each stove from the main when and as required. As the apparatus to which reference has just been made is of the usual type found in the blast furnace plants, it is believed no further description thereof is necessary herein and it will be understood that the relations of the several units to each other is indicated as rectilinear for convenience only, as in some plants the stoves are arranged at other points with respect to the furnace or to each other, but in any case the stoves are ordinarily each connected to a hot blast main leading to the furnace and to a sewer leading to the stack, the particular design, construction and arrangement. of these elements, however, forming no part of the present invention, It will also be understood that blast furnace installations of this general type are also provided with a suitable blower (not shown) or other means for introducing airv under pressure into the stoves 2 and suitable valves interposed in the system to permit the air fromthe blower to bedischarged into the atmosphere instead of through thestoves when the furnace is to be back drafted.

In our invention we eliminate the necessity of passing the gases withdrawn from the furnace through one or more of' the stoves by providing a section of pipe 8 connected to the hot blast main in such way as to form an airtight joint therewith, desirably at a polnt closely adj acent the stack 6, while a similar section of pipe 9 is interconnected'with the stack so as to extend outwardly therefrom in substantial alignment with the pipe 8, the .pipes 8 and 9 being interconnected through the interposition between them of a suitable valve or damper 10 which may be of' any desired construction suitable for affording a substantially unrestricted passage through the pipes Band 9 from the hot blast main 3 to the stack 6 when the valve is open and for closing the said passage and preventing the escape of air or gas-from the main to the fstack when the valve is closed. Although We may employ a manually operable valve,

it will be understood that mechanism or other means (not shown) for effecting the opening and closing of the valve will usually be provided.

I With an installationof this character it is apparent that when the air from'the blower is diverted from its usual course and is discharged into the atmosphere or elsewhere other than through the stoves,and valve 1 0is opened, a free passage is afforded for the furnace gases directly into the stack through I the pipes 8 and 9 and the valve 10, whereby the pressure in the furnace is rapidly relieved as the gases aredrawn therefrom by the natural draft of the stack supplemented by the initial pressure of the gases themselves, so that very shortly after the valve-10 is opened, one or more tuyeres can be removed or openings otherwise created in the It will furthermore be apparent that the resistance to the movement of the gases from the furnace through the hot blast main, past the valve 10 and into the stack is relatively negligible compared to that offered by the checker Work in one or more of the hot stoves 1 when the back drafting operation is carried out in the manner heretofore practiced. Particularly is this true when the checker work within the stove is of such character as to afford tortuous passages of relatively small size for traverse by the gases, or when the passagesin the checker work through long use have become more or less clogged with dust and the like, for while under these conditions no material difiiculty is encountered in forcing air through the checker work under the high pressures employed in the normal operation of the furnace, the relatively slight natural draft afforded by the stack, even when supplemented at the initiation of the back drafting operation by the pressure of the gases within the furnace, is. insuflicient to carry the gases through the checker worlc of the stove with sufiicient rapidity to properly. relieve the pressure within the furnace, which is the sole and ultimate object of the back drafting operation. Therefore, since the resistance offered to the passage of the gases through the stove is materially greater than that offered by the pipes 8, 9 and valve 10 when the latter are provided in accordance with ourinvention, it is frequently found unnecessary to interrupt the normal connection between one or more of the stoves and the hot blast main or to Open,

the valves between one or more of the stoves and the sewer 5 while the back drafting is being performed in accordance with our improved method.

Since the only moving part requisite for the practice of our invention is the valve 10, which can readily be constructed in a manner to satisfactorily withstand the uses to which it is to be subjected, and as the valve and associated parts may be of an extremely simple nature, the use of our invention in no way enhances the difliculty of the operation of the furnace as a whole nor involves any large initial outlay or the necessity for frequent repairs or replacements with resulting enhancement of production cost.

lVhile we have herein described our invention with some particularity both as to the method comprised therein and the means which we prefer to employ, it will be understood that we do not intend to limit or confine ourselves specifically thereto in any way as many changes and modifications 1n the form, construction and arrangement of the several parts of our apparatus and in the manner of performing our improved method will readily occur to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described our invention, we claim and desire to protect by Letters Patent of the United States:

1. The combination with a blast furnace, a hot blast main interconnected therewith and a stack, of a pipe extending between said hot blast main and said stack and a valve interposed in said pipe and operable to control the passage through said pipe between the hot blast main and the stack.

2. In combination with a blast furnace, a hot blast main interconnected therewith and a stack, said hot blast main being normall operative to conduct the blast to the blast furnace, means extending between saidmain.

7 through during the normal operation of the furnace.

4. In blast furnace operation, the method of back drafting which comprises the step of inducing a fiow of gases from the furnace through the hot blast main and thence dinormal fiow of the blast therein.

6. That method of back drafting a blast furnace which consists in by-passing the gases from the furnace through the hot main and thence directly to the stack while maintaining the connections between the hot stoves andv the stack in the same condition as at the initiation of the back drafting operation.

7 That method of back drafting a blast furnace which consists in forming a direct passage for the furnace gases from the hot main to the stack while leaving the connections between the hot stoves and the stack in the same condition as that maintained when air is being carried through said stoves during normal operation of the furnace.

In'witness whereof, we have hereunto set our hands this 21st day of September, 1931.

" CHARLES H. HEIST.

BUFORD M. STUBBLEFIELD. 

